1. Field of the Invention
The present invention relates to a video signal processing apparatus, an imaging apparatus, a video signal processing method, and a computer program, and in particular to a technology for adjusting a gamma curve used during gamma correction.
2. Description of the Related Art
Although display apparatuses such as CRT (Cathode Ray Tubes) and LCD (Liquid Crystal Displays) display images in accordance with an inputted video signal, even when the same image is displayed by different display apparatuses, the brightness and chroma of the image displayed on the screen may differ between apparatuses. This is because gamma characteristics that express the luminance reproduction characteristics during photoelectric conversion may differ due to factors such as the type of elements that form the screens of the display apparatuses. For this reason, gamma correction that adjusts the respective tone values of an input image to suitable values for the gamma characteristics is carried out so as to reproduce the luminances of the original image on a display apparatus.
Gamma characteristics are expressed by a gamma curve that shows the ratio of the brightness of outputted video to the signal level of inputted video. Therefore, to carry out gamma correction, the gradient of the gamma curve is adjusted in advance with consideration to the input/output characteristics of the display apparatus and the tone values in the input video signal are converted in accordance with the adjusted gamma curve.
In recent years, demand has also emerged for a technology capable of changing the tone reproduction of images displayed on the screen of a display apparatus, such as a change in accordance with the type of scene being reproduced by images. In such case also, the intended color reproduction is achieved by adjusting the gamma curve.
For example, Japanese Unexamined Patent Application Publication No. 2007-60393 discloses a technology that makes it possible to change the positions of a number of points that form a gamma curve by moving sliders, and carries out gamma correction using the adjusted gamma curve.